Terrestrial Ecotoxicity of Eight Chemicals in a Systematic Approach (7 pp)

Background and Objective   Terrestrial ecotoxicity data are required for many research purposes. The data are derived either from the literature or elaborated by own investigations. As the terrestrial toxicity tests are usually time-consuming and labour intensive, the experiments are performed with a limited number of test organisms and soils. In the context of a project sponsored by CEFIC-LRI (European Chemical Industry Council – Long-Range Research Initiative), EC50-values were systematically elaborated for eight chemicals with a wide range of logKow-values (CdCl2, Trinitrotoluene, 3,4-dichloroaniline, 2,4-dichlorophenol, Tributyltinchloride, Pentachlorophenol, Benzo(a)pyrene, p,p-dichloro-2,2-diphenyl-1,1,1-trichloroethane). The substances were selected covering a broad range of physico-chemical and ecotoxicological properties. As toxicity endpoints, microbial activities, plant germination and growth as well as reproduction of earthworms and collembola were determined. As such systematic investigations are rarely performed and for some substances no data existed, the data pool is made available to the scientific community.Methods   All toxicity tests were conducted on three different soil types (sandy soil, silty soil, loamy soil), according to ISO and OECD guidelines Results, Discussion, Conclusion and Outlook   The different toxicities of the chemicals, the influence of soil properties on bioavailability as well as different sensitivities of test organisms and test parameters are reflected by the EC50-values. The results showed that the EC50-values calculated on the basis of nominal concentrations can significantly vary from EC50-values derived from analytical concentrations for some substances. To avoid false conclusions, this has to be considered especially when concentrations determined in the field are compared with toxicity data obtained from the literature or calculated on the basis of nominal concentrations. Moreover, the results indicate that terrestrial ecotoxicological tests should be accompanied by chemical analyses, to be sure to derive sound EC50-values. As the tests were performed according to international guidelines, the comprehensive data pool relevant for the terrestrial ecotoxicity of eight chemicals is considered to be of great value for further research and discussions dealing with the habitat function of soils.     

Acute and chronic isopod testing using tropical Porcellionides pruinosus and three model pesticides

An approach for testing acute and chronic ecotoxicological effects of pesticides on isopods in the laboratory is presented. Laboratory cultures of tropical Porcellionides pruinosus were used. The pesticides Benomyl, Carbendazim and lambda-Cyhalothrin served as model chemicals. The toxicity tests were done with five to six concentrations and one untreated control in four replicates containing 10 individuals per vessel. The test was performed at 28 °C, in permanent darkness and it lasted 14 days. Each chemical was mixed in 250 g DW per vessel of OECD artificial, LUFA 2.2 standard, tropical artificial or tropical natural soil in acute tests. Chronic tests were performed using 150 g DW OECD artificial or LUFA 2.2 standard soil. Both adult mortality and number of juveniles showed a high sensitivity of P. pruinosus towards lambda-Cyhalothrin while Carbendazim and Benomyl had a very low and no toxicity, respectively. Further research and optimization of the chronic test design are required.     

Ecotoxicity of Alternative De-icers

Background  De-icers are essential to wintertime road maintenance in Nordic countries. The use of road salts (NaCl, CaCl₂ and MgCl₂) is having significant effects on groundwater. There has been a growing concern of environmental effects resulting from de-icing. Regulatory bodies have tried to find de-icers which have less harmful impacts on soil and groundwater. Alternative new organic de-icers are e.g. potassium formiate, potassium acetate, and calcium magnesium acetate. Objectives  At present, the decision finding for soil and water quality assessment is mainly based on the results of chemical analyses. However, ecotoxicological characterization will provide more useful information for determining environmental effects of de-icers. Methods  Six different de-icers, NaCl, CaCl₂, MgCl₂, potassium formicate KFo, potassium acetate KAc and calcium magnesium acetate CMA were studied with different bioassays. These bioassays were two plant tests (onion Allium cepa root elongation test and duckweed Lemna growth inhibition test), an enzyme inhibition test (reverse electron transport test, RET) and a microbial test (luminescent bacteria Vibrio fischeri, BioTox test). Results and Discussion  Most of the responses of the de-icers tested were toxic to test organisms. CMA was unsuitable for RET and BioTox tests because it was not possible to analyze turbid samples with these bioassays. On the whole, organic chemicals were more toxic than the inorganic salts. According to the Lemna and Allium cepa tests KFo was the most toxic and the toxicity ranking of the de-icers was KFo > KAc > CMA > CaCl₂ > NaCl > MgCl_2. The sensitivity ranking for tests in decreasing order was Lemna > Allium cepa > RET > BioTox. The plant tests proved to be relevant, easy, cost-effective and sensitive screening methods of de-icers: Lemna test was 92 times more sensitive and Allium test 70 times more sensitive than BioTox to KFo. Conclusion and Outlook  The tested de-icers had significant effects on plant growth, microbial luminescence and enzymatic activity. Toxicity could hardly be predicted from the chemical concentrations of these de-icers. In summary, these results demonstrate a need for including toxicity measurements in the evaluation of technologies used in soil treatment and illustrate the potential value of such measurements for ensuring that no or minimal environmental contamination would arise from de-icing process.     

Sediment toxicity and heavy metals in eleven lime reference lakes of Sweden

Sediments from an eutrophic reference lake (L. HjÄlmaren) and eleven oligotrophic Swedish lakes were analyzed for heavy metals (Cd, Cr, Cu, Hg, Ni, Pb, and Zn) and tested for whole sediment toxicity to Daphnia magna. Whole sediment toxicity, expressed as 48-hr EC50 on a wet weight basis in reconstituted dilution water, ranged from 2.8% (most toxic) to >32% (least toxic). Correlations between bulk sediment heavy metal concentrations and toxicity were significant (P≤0.05) for Hg, Pb, and Zn. However, a causal connection between the concentrations of these metals and toxicity was not supported by the results from metal-spiked sediment toxicity tests. In addition sediment toxicity was not affected by the addition of EDTA, which is a strong chelator known to reduce metal toxicity. After storage for several months test sediments either remained nontoxic, toxic, or increased in toxicity. These results illustrate some of the difficulties in the interpretation of bulk sediment chemistry data and the release of toxic chemicals from sediment samples, highlighting the effect of sediment storage on toxicity.     

Comparisons of terrestrial and aquatic bioassays for oil-contaminated soil toxicity

Background  Petroleum products are widely used in various sections of industry and they are one of the most abundant sources of environmental contamination. These products are classified by their physico-chemical properties such as boiling point, density and viscosity. Oil contamination in the environment is primarily evaluated by measuring the chemical concentrations of petroleum products in the solid or water phase. The results of chemical analyses do not correspond directly with the harmful environmental effects of petroleum products on the soil flora and fauna, because the interactions between oil compounds and the production of their methabolites in soil are not measured in chemical assessments. These kinds of effects of complex chemical mixtures in soil can be estimated by bioassays. Therefore, ecotoxicological tests are important for estimating soil quality in the risk assessment of oil-contaminated soil sites. Objectives  The objective of this study was to examine the oil-contaminated soil site of a closed petrol station with both chemical and ecotoxicological methods. The goals of this study were to compare the sensitivity of the terrestrial and aquatic bioassays and to compare the toxicity responses of aquatic bioassays determined from three different extraction procedures. In addition, our aim was to characterise a cost-effective battery of bioassays that could be applied to a comparison of oil-contaminated soils. It was in our interest to investigate oil-contaminated soil with oil concentrations of 2500–12000 mg/kg and to find out the possible differences between terrestrial and aquatic toxicity tests. Methods  Six soil samples from a closed petrol station were examined for toxicity with terrestrial and aquatic tests. Terrestrial tests includedEnchytraeus albidus survival and reproduction assays and seed germination assays using wheat, cress, lettuce, and red clover seeds and growth inhibition assays of onions. The toxicities of the water-extractable fractions of the soil samples obtained from three different extractions were tested with aquatic bioassays based on plants (onion and duckweed growth inhibition tests), microbes (luminescent bacteria test), and enzyme inhibition (reverse electron transport test, RET). Chemical analyses of the solid samples were carried out simultaneously. Results. Oil concentrations ranged from 2500 to 12000 mg/kg, BTEX varied from 300 to 2800 mg/kg, and fuel additives: MTBE and TAME from 0.0 1 to 260 mg/kg. Only the sample contain-ing 12000 mg/kg oil had a significant toxic impact on all test organisms. Soil samples with oil concentrations 2500–6200 mg/ kg had no or only slight adverse effects on the test organisms with one exception, theE. albidus reproduction test. TheE. albidus survival and reproduction tests were the most sensitive bioassays of the terrestrial tests, and the luminescent bacteria test of the aquatic tests.     

Validation of Microplate Bioassays for the Assessment of Contaminated and Remediated Sites

Background, Goal and Scope  Bioassays are frequently used to investigate the water extractable ecotoxicological and genotoxicological potential of contaminated soil samples. A laboratory intercomparison study was performed for validation of miniaturised biological test systems for the assessment of contaminated and remediated sites. The successful performance of this study resulted in an optimisation of microplate assays with respect to the testing of chemicals and environmental samples. Methods  For this purpose, miniaturised bioassays were chosen, which, because of their stage of development, are suitable for routine application in the characterisation of the water extractable ecotoxicological and genotoxicological potential of soils. These ecotoxicological and genotoxicological assays were performed with contaminated soil samples by three institutions at the same time. Results and Discussion  The toxicological assessment of the contaminated and remediated soil samples using LID-values, as a rule, was highly uniform. Some minor deviations could, for the most part, be explained by the heterogeneity of the soil samples and, to a lesser extent, by methodical aspects. The difference in sensitivity towards contaminants of the two bacteria Vibrio fischeri and Pseudomonas putida was pointed out. In the algae test with Desmodesmus subspicatus, the influence of the highest sample concentrations on the growth controls became obvious. It was recommended to modify the experimental setup of the microtitration plate, i.e. to place growth controls located next to both the lowest and the highest dilution steps of the sample. The Ames-test did in some cases provide new information on the genotoxicity of the samples, but is not considered useful in a test battery for the evaluation of the genotoxic potential because of its great expense in time and work. Conclusions  The investigations in this laboratory-intercomparison study for the assessment of the water extractable toxic potential of soil samples show that different bioassays are needed, which, in contrast to chemical-analytical methods, can detect the complete effects of all present pollutants in contaminated and remediated soils and solid substrates path-specifically. Recommendations and Outlook  If the recommended modifications for the performance of the bacterial and algae growth inhibition assays on microplates are taken into consideration, these tests can substitute the tests performed on a macro scale. The usefulness of the umu-test and the NM2009-test for the investigation of the genotoxic potential has been proven. Although the tests performed on microplates require much lower sample amounts, it is recommended that sample amounts be eluted in accordance with current guidelines to ensure representativity of the sample. Further work should focus on toxicity identification studies in the future by combining chemical and toxicological analyses.     

轮耕对渭北旱塬春玉米田土壤理化性状和产量的影响

为了揭示不同轮耕处理对渭北旱塬春玉米田土壤理化性状及春玉米产量的影响,于2008—2010年在陕西合阳设置了免耕深松免耕(NT/ST/NT)、深松翻耕深松(ST/CT/ST)、翻耕免耕翻耕(CT/NT/CT)、免耕免耕免耕(NT/NT/NT)、深松深松深松(ST/ST/ST)和翻耕翻耕翻耕(CT/CT/CT)6种轮耕模式,测定和分析了各轮耕处理下土壤容重、土壤养分与玉米产量差异。结果表明:(1)各轮耕处理降低了土壤容重,提高了土壤孔隙度,增加了田间持水量,且以NT/ST/NT处理效果最佳;与对照CT/CT/CT相比,NT/ST/NT处理0～20cm和20～40 cm土层土壤容重分别降低11.43%和9.79%,土壤孔隙度分别增加11.05%和9.87%。(2)NT/ST/NT处理对耕层0～20 cm土层土壤有机质和全氮含量影响显著(P<0.05),0～60 cm土层土壤有机质平均含量最高(10.36 g.kg 1),土壤全氮含量平均值比试验开始前和对照CT/CT/CT分别提高10.65%和4.31%;各耕作处理对0～20 cm土层土壤全氮和碱解氮含量影响较大,而对20～40 cm土层土壤有效磷和速效钾含量影响较大,保护性轮耕处理对土壤培肥效应显著(P<0.05)高于传统翻耕处理。(3)NT/ST/NT、ST/CT/ST、CT/NT/CT、NT/NT/NT和ST/ST/ST处理产量比对照CT/CT/CT处理分别增产22.42%、16.33%、3.77%、9.91%和14.18%(P<0.05),以NT/ST/NT处理春玉米增产率最高。     

The detection of mutagenic pollutants in marine organisms of Kuwait

Several types of pollutants are currently entering the territorial waters of Kuwait from a variety of sources. Some pollutants, especially petrochemicals, are known to be potentially mutagenic and/or carcinogenic. Some of these chemical pollutants may enter the tissues of aquatic organisms and eventually the human body. The presence of such chemicals in the marine environment might create a serious health hazard. The marine environment of Kuwait was monitored for the presence of mutagenic chemicals using living organisms such as shrimp, clams and algae as bioindicators. These organisms were collected from selected sites within Kuwait territorial waters. Their tissues were extracted in ethanol and screened for genetically active chemicals by two standard bacterial assays, the Fluctuation Test and the Ames Test. Salmonella typhimurium TA98 was used as a tester strain. The data obtained from this study indicated that the shrimp, algae and clam samples were polluted with low concentration of frameshift mutagens. Due to the limited scope and nature of this study it was impossible to determine the source(s) of input or the chemical nature of these pollutants.     

The influence of soil characteristics on the toxicity of four chemicals to the earthworm Eisenia fetida andrei (Oligochaeta)

Summary The acute toxicity of Cd (chloride), chloroacetamide, 3,4-dichloroaniline and pentachlorophenol to the earthworm Eisenia fetida andrei was determined using the OECD (1984) artificial soil and contact testing procedures. To investigate the influence of two soil characteristics (pH and organic-matter content), the toxicity of the chemicals was also determined in two natural sandy soils. It is concluded that the filter-paper contact test cannot be recommended to predict earthworm toxicity of these chemicals in soil. Toxicity in soil was influenced by both pH and organic-matter content. Differences between LC₅₀ values in the high-organic-matter artificial soil and in an acid, low-organic-matter sandy soil were, however, not greater than a factor of 3–4. The results of this study therefore support the use of a well-defined artificial soil substrate for standardized earthworm toxicity tests.     

Biotest— and chemistry-based hazard assessment of soils,sediments and solid wastes

Background and Objectives  The current environmental legislation regulating pollution issues is based on total levels of pollutants. This approach is not taking into account the bioavailability of pollutants (that is especially important for an analysis of soils and sediments as heavy metals and hydrophobic organic toxicants tend to sorb to solid matrix) and effects of toxicants in mixtures. Thus, toxicity-based criteria should be added to the currently existing chemical ones for the meaningful evaluation of the environmental hazard. The aim of the current study was 1) to compare the ecotoxicity and chemistry-based environmental evaluations for 27 solid-phase environmental samples (soils, sediments, solid wastes); 2) to suggest the battery of biotests for the screening of water-extracted toxicity. Methods  14 soils, 9 sediments and 4 oil-shale industry solid waste samples from Estonia and Lithuania were analyzed for the concentration of total PAHs, heavy metals, oil products and water-extracted phenols. The pollution level was evaluated by comparison of measured concentrations with Estonian permitted limit values in residential (PLV_r) and industrial (PLV_i) areas for each key pollutant A battery of 8 aquatic toxicity tests was applied for the analysis of aqueous extracts (L/S=3) of samples: tests with microalgaeSelenastrum capricornutum, macroalgaeNitellopsis obtusa, protozoaTetrahymena thermophila, crustaceansDaphnia magna andThamnocephalus platyurus, rotifersBrachionus calyciflorus and photobacteriaVibrio fiscberi. Particle-bound bioavailable toxicity was evaluated using a kinetic photobacterial assay withVibrio fiscberi (Solid-Phase Flash-Assay). The toxicity data were evaluated by MaxTox index (highest toxic signal of the battery). Results  Chemical evaluation and toxicological evaluation pointed to the same direction in half of the cases (13/27): 5 samples (including 2 presumably clean control soils) proved harmless and 8 hazardous to environment in case of both evaluations. However, there was a disagreement between chemical and toxicological evaluations for the rest of the samples (14/27). In two mismatching cases (soils from the territory of former gasoline stations) the level of oil products exceeded the PLV_r, but no toxicity was detected, most probably due to the low bioavailability of aged pollutants. It must be taken as a warning that a majority of mismatching cases (12/14) of the samples proved to be toxic or even very toxic despite the fact that the measured hazardous key pollutant levels were below the PLVr. Within these 12 samples were 2 soils from municipal dumping sites, 2 soils from the territory of military airport, 6 sediments from Curonian lagoon (Lithuania) and 2 oil-shale industry solid wastes (Estonia). Conclusions  The results of this study show the necessity of biotesting in environmental risk assessment to avoid the falsenegative results that may result in harmful effects for the ecosystems and also to human health. The following, reduced test battery was proposed for the ecotoxicological hazard assessment of water-extractable toxicity of solid-phase samples:Tetrahymena thermophila growth inhibition assay,Daphnia magna mortality assay andSelenastrum capricornutum growth inhibition assay. Also, the Microtox test (Vibrio fiscberi luminescence inhibition assay) could be valuable for screening purposes. For the evaluation of particle-bound, bioavailable toxicity of soil suspensions, Solid-Phase Flash-Assay (test organismVibrio fiscberi) is suggested. Compared to the results obtained with the initial battery of 8 tests, the reduced battery detected the toxicity in 85% of the cases.     

Influence of Mechanical-Biological Pretreatment On the Toxicity of Municipal Solid Waste

Mechanical-biologically pretreated residual waste was tested for toxicity, chemical quality and reactional behavior. Samples were taken from different composting plants at different stages of treatment. Acute toxicity was determined using Daphnia magna (crustacean) and Vibrio fischeri (luminescent bacteria), chronic toxicity was tested with Selenastrum capricomutum (green algae) and Lepidium sativum (cress). Samples were analyzed for various physico-chemical parameters and for biological parameters (respiration activity, gas-generating potential). Toxicity tests were carried out from eluates and toxicity was expressed in German regulatory G-values. The results of this study indicate that high toxicity was observed in untreated MSW samples and in samples with a short treatment period. In most cases toxicity decreased significantly when the treatment period increased and marked differences were observed in the susceptibility among the species. Toxicity varied between a G-value of 1 and 256. For some tests a good relationship was noted between toxicity and high results of conductivity, TOC, COD, BOD5 and biological tests. It was found that high toxicity can influence biological tests, resulting in longer lag-phases and thus leading to misinterpretation.     

Evaluating soluble toxicants in contaminated soils

Complex mixtures of water soluble materials from contaminated soils can move into groundwater and surface water by leaching, percolation, and runoff. We evaluated the potential toxicity of leachable materials from seven soils. Five soil samples were obtained at designated toxic or hazardous waste sites, and two additional soils samples were obtained from a coal storage area and from an agricultural field. Acidified tap water (pH 4.5) was used to extract toxic materials from elution columns filled with soil samples. Extracts were used as complex mixtures to conduct acute toxicity tests using Daphnia and chronic effects tests using aquatic microcosms. Three classes of effects were observed. Three soil leachates showed acute and chronic toxicity at less than 3% leachate. Two of these soils were contaminated by materials used in wood preserving, and the third soil was contaminated with heavy metals and acid. Two soils showed moderate acute toxicity but no chronic toxicity in microcosm tests. One of these soils was contaminated with low levels of chromium while the other soil was from a coal storage area. The remaining two soil samples showed no toxicity in either acute or chronic toxicity tests. One of these soils was from a reference agricultural field while the other soil was contaminated with solvents. The failure to detect toxicity in the solvent contaminated sample was attributed to the hydrophobicity of the toxicity materials. Results of these toxic screenings are in the same range as leachate toxicities estimated using other methods, although other methods use extraction materials that may interfere with some biological tests. Toxicological evaluations of materials from suspected contaminated soil are recommended for prioritizing clean up efforts at waste sites and for determining if toxic materials and contaminated soils have been effectively removed.     

Hazard identification of contaminated sites—ranking potential toxicity of organic sediment extracts in crustacean and fish

Background, aim, and scope  It is well known that contaminated sediments represent a potential long-term source of pollutants to the aquatic environment. To protect human and ecosystem health, it is becoming common to remediate contaminated sites. However, the great cost associated with, e.g., dredging in combination with the large numbers of contaminated sites makes it crucial to pinpoint those sites that are in greatest need of remediation. In most European countries, this prioritization process has almost exclusively been based on chemical analyses of known substances; only seldom toxicity data has been considered. The main objective of the current study was therefore to develop a tool for hazard identification of sediment by ranking potential toxicity of organic sediment extracts in a crustacean and a fish. A secondary objective was to investigate the difference in potential toxicity between compounds with different polarities. Materials and methods  Early life stages of the crustacean Nitocra spinipes and the fish Oncorhynchus mykiss, which represent organisms from different trophic levels (primary and secondary consumer) and with different routes of exposure (i.e., ingestion through food, diffusive uptake, and maternal transfer), were exposed to hexane and acetone fractions (semi-polar compounds) of sediment from five locations, ranging from heavily to low contaminated. Preliminary tests showed that the extracts were non-bioavailable to the crustacean when exposed via water, and the extracts were therefore loaded on silica gel. Rainbow trout embryos were exposed using nano-injection technique. Results and discussion  Clear concentration–response relationships of both mortality and larval development were observed in all tests with N. spinipes. Also for rainbow trout, the observed effects (e.g., abnormality, hemorrhage, asymmetric yolk sac) followed a dose-related pattern. Interestingly, our results indicate that some of the locations contained toxic semi-polar compounds, which are normally not considered in risk assessment of sediment since they are focused on compounds isolated in the hexane fraction. Conclusions  The ranking of the five sediments followed the expected pattern of potential toxicity in both organisms, i.e., sediments with known pollution history caused major effects while reference sediments caused minor effects in the two test systems. Silica gel turned out to be an excellent carrier for exposure of N. spinipes to very hydrophobic and otherwise non-bioavailable sediment extracts. Recommendations and perspectives  Since both test systems demonstrated that a substantial part of the potential toxicity was caused by semi-polar compounds in the acetone fractions, this study enlightens our poor understanding of which compounds are causing adverse effects in environmental samples. Therefore, by investigating potential toxicity (i.e., hazard identification) as a first screening step in prioritizing processes, these implications could be avoided. For proper sediment risk assessment, we however recommend whole sediment toxicity tests to be used for selected sites at following tiers.     

不同轮耕方式对渭北旱塬麦玉轮作田土壤物理性状与产量的影响

为研究不同轮作模式对渭北旱作冬小麦?春玉米一年1熟轮作田土壤物理性状和产量的影响,于2007—2014年在陕西省合阳县冬小麦?春玉米轮作田连续7年实施了保护性耕作定位试验,测定和分析了免耕/深松、深松/翻耕、翻耕/免耕、连续免耕、连续深松和连续翻耕6种轮耕模式下麦田0~60 cm土层物理性状、0~200 cm土层土壤湿度和小麦产量的变化。结果表明:1)不同轮耕模式0~40 cm土层土壤容重、孔隙度和田间持水量差异显著,其中以免耕/深松效果最显著;0~60 cm土层免耕/深松轮耕处理平均田间持水量较连续翻耕处理提高12.9%;2)轮耕对土壤团聚体特性影响明显,免耕/深松0.25 mm水稳性团聚体含量(R0.25)最高,结构体破碎率和不稳定团粒指数(ELT)最低,水稳性均重直径(WMWD)最高,水稳性和力稳性团聚体分形维数(D)均最低;3)小麦生育期间免耕/深松处理0~200 cm土层土壤蓄水量和小麦产量较连续翻耕分别增加17.7 mm和9.5%。综合可知,轮耕有利于耕层土壤物理结构改善,免耕/深松更有利于耕层土壤大团聚体形成和土壤结构稳定,利于土壤蓄水保墒和作物增产,为渭北旱塬区麦玉轮作田较适宜的轮耕模式。     

Toxicity reduction of Ontario hydro radioactive liquid waste

The radioactive liquid waste (RLW) system in Ontario Hydro's pressurised heavy water reactors collects drainage from a variety of sources ranging from floor drains to laundry waste. RLW effluent was intermittently toxic to rainbow trout andDaphnia magna during the first phase of Ontario's Municipal Industrial Strategy for Abatement (MISA) Program, apparently as a result of the interaction of a variety of known and unknown organic and inorganic compounds. Accordingly, we employed a tmatment-based approach to reducing its toxicity, supplemented by chemical analysis. Two series of toxicity reduction tests were conducted. The fast series explored the potential for sorption of the possible toxicants, while the accord series incorporated a wider variety of treatments. Of the 24 samples in the first test series, 17 were toxic (D. magna mortality ≥ 50%). Of the toxic samples, only 7 of 17 were still toxic after passage through an activated carbon column, but 5 of 6 samples tested remained toxic after passage through a metal chelating resin column. In the second series, at least one of the treatments was effective in reducing toxicity of all samples which were initially toxic (16 of 24 samples), but no one treatment was effective for all toxic samples. Three treatments (UV/H₂O₂ photo-oxidation with prior pH adjustment, or passage through a column of either a non-functioalized (N-F) resin or a mixture of N-F resin and a weak base (W-B) anion exchange rain), were effective in reducing the toxicity of more than 50% of the toxic samples; yet roughly 25% of these samples remained toxic after treatment O₂ sparging, UV/H₂O₂ photo-oxidation without prior pH adjustment, and passage through a column of the W-B Resin were less effective, as more than 50% of the samples remained toxic after treatment. Filtering was not effective, as all of the treated samples (9/9) retained their toxicity. There was no obvious correspondence between toxicity and the concentrations of metals (Cu, Zn, Fe, Al and Cd) nor were any simple relationships apparent between toxicity and Total Organic Carbon or NH₃ concentrations. At stations where radioactive liquid wastes are segregated, toxicity was also segregated, suggesting that we may be able to address the problem at source through a combination of Best Management Practices and smaller scale treatment facilities.     

Toxicity Studies in a Tobacco Industry Biological Treatment Plant

Tobacco industry wastewater contains some toxic contaminantswhich inhibit the microbial consortium in biological treatmentplants. Investigations carried out showed that the most important sources of these toxic contaminants are nicotine,flavoring chemicals containing glycogen and alcohol, absorbableorganic halogens (AOX), and pesticides from tobacco leaves. Shock loadings of these toxic contaminants inhibit the bacterialactivity during biological treatment. Input of wastewater containing such toxic substances causes decreases in bacteria numbers and reduce the treatment efficiency in the treatmentplant. Viable numbers of floc forming, total and faecal coliform bacteria which are living in a biological treatmentunit (i.e. Biopac) were monitored. Conventional short-term bioassays and enrichment toxicity tests were performed to determine potential toxicity. If the ratio of bacteria numbersgrowing in the enrichment medium compared to control is between0.8 and 1.2, it may be assumed that toxic substances are absent.If this ratio exceeds 1.2, it may be assumed that growth stimulating substances are present. If this ratio is below 0.8,this indicates the presence of toxic substances. The results ofenrichment toxicity studies showed that enough nutrients canstimulate the bacterial growth, or known/unknown sources of toxicity can be inhibit the microbial growth. Furthermore, results of chemical coagulation/flocculation test experimentsshowed that chemical treatment is effective at reducing toxicityand is proposed for biological treatment.     

Survey of Nutrient Status in Vitis vinifera Grapes in North Carolina

Grape (Vitis vinifera L.) production is a rapidly growing industry in North Carolina; however, no local-research-based information is available to support nutrient-management decisions. Field studies were initiated to survey soil and plant nutrient status over a wide range in geography and management conditions in the dominant V. vinifera regions in North Carolina. While the survey data are still being analyzed, significant information was initially obtained to identify aluminum toxicity and phosphorus and potassium deficiency as potential limiting factors to vine health and productivity. Field studies were initiated to quantify soil test and plant nutrient responses to lime, phosphorus, and potassium rates. Responses to phosphorus and potassium application were observed at most sites predicted by soil tests. However, lime responses were not observed in either petiole or blade samples collected at full bloom or veraison. These studies will be continued until sufficient response data are collected to establish soil test and plant nutrient diagnostic criteria for efficient nutrient management of V. vinifera in North Carolina.     

Effects of rotational tillage practices on soil structure,organic carbon concentration and crop yields in semi‐arid areas of northwest China

Continuous conventional tillage can cause serious soil degradation in rain‐fed agriculture, which reduces crop productivity. Adopting suitable tillage practices is very important for improving the soil and increasing crop productivity. Between 2007 and 2010, a 3‐year field study was conducted in semi‐arid areas of southern Ningxia, China, to determine the effects of rotational tillage practices on bulk density, soil aggregate, organic carbon concentration and crop yields. Three tillage treatments were tested: no‐tillage the first and third year and subsoiling the second year (NT/ST/NT); subsoiling the first and third year and no‐tillage the second year (ST/NT/ST); and conventional tillage each year (CT). A conventional tillage treatment was used as the control. Under the rotational tillage treatments, the mean soil bulk density at a depth of 0–60 cm was significantly (P < 0.05) decreased by 4.9% compared with CT, and with the best effect under ST/NT/ST. The soil organic carbon (SOC) concentration and aggregate size fractions and stability at 0–40 cm depth were significantly (P < 0.05) increased in rotational tillage treatments when compared with the conventional tillage, and the ST/NT/ST treatment produced the highest increases. Significant differences were detected in the SOC concentration in 2 to 0.25–mm size fractions at 0–30 cm depth between rotational tillage treatments and conventional tillage. Biomass and grain yield with the rotational tillage practices were significantly positively influenced over 3 years, and ST/NT/ST produced the highest average crop yields among the three treatments. Therefore, it was concluded that the application of rotational tillage with subsoiling every 2 years and no‐tillage every other year (ST/NT/ST) should be of benefit in promoting the development of dryland farming in semi‐arid areas of northwest China.     

Preliminary assessment of metal toxicity in the middle tisza river (Hungary) flood plain

Cyanide and heavy metals were accidentally released from a mine waste lagoon in Romania into tributaries ultimately draining into the Tisza River. Within two months of the cyanide accident two subsequent heavy metal waste spills further contaminated the Tisza River, followed by severe spring flooding, which potentially spread the contamination to soils adjacent to the river. Flood plain soils and shoreline sediments were sampled from two locations on the middle Tisza River and a reference site to conduct a preliminary assessment of metal content and toxicity. Ten-day sediment toxicity tests were conducted with the amphipod,Hyalella azteca and 24 h soil toxicity tests were conducted with the nematode (Caenorhabditis elegans). High concentrations of cadmium, copper, zinc, lead and arsenic were detected in soil and sediment samples. However, no mortality was observed inHyalella exposed to Tisza River sediments and only up to 27% mortality of C.elegans was observed in flood plain soils. Low mortalities are attributed to reduced metal bioavailability caused by high soil cation exchange capacities and possible interactions with sediment organic matter or sulfides. Future studies should focus on factors that alter metal bioavailability and their relationship to potential toxicity of organisms exposed to Tisza River sediments and flood plain soils.     

Botanical pesticides and their human health safety on the example of Citrus sinensis essential oil and Oulema melanopus under laboratory conditions

Biopesticides derived from plants have recently received increasing interest as an alternative to conventional chemicals suitable for integrated pest management and organic farming. In this study, Citrus sinensis (Osbeck) essential oil was tested for its potential for wheat protection against Oulema melanopus (L.). The chemical composition of the essential oil was analyzed by gas chromatography-mass spectrometry (GC-MS). Twenty-four compounds were identified in the oil among which d-limonene was a predominant component, followed by myrcene, α-pinene, linalool, sabinene, decanal, and other minor components. Direct contact toxicity assay showed the effectiveness of the essential oil against O. melanopus larvae causing the mortality of 85% during 48 hours. The persistence study revealed high dissipation rate of the oil from treated plants, whereas concentrations lower than 0.01 g/kg were detected by GC-MS 5 min after the application of the oil, suggesting its environmental and food safety. These results, together with previous literature reports reviewed in this study, indicate the great potential of the C. sinensis essential oil for future use in crop protection against insect pests.